The timing of the strike on the air base in the central Homs province, hours after President Donald Trump said there would be “a big price to pay” for the chemical weapons attack, raised questions about whether Israel was acting alone or as a proxy for the United States.

The Associated Press

BEIRUT — Russia and the Syrian military blamed Israel for a pre-dawn missile attack Monday on a Syrian air base that reportedly killed 14 people, including three Iranians, while international condemnation grew over a suspected poison gas attack over the weekend that was said to be carried out by the Syrian government.

Opposition activists said 40 people died in the chemical attack, blaming President Bashar Assad’s forces. The U.N. Security Council planned to hold an emergency meeting Monday to discuss the chemical attack.

The timing of the strike on the air base in the central Homs province, hours after President Donald Trump said there would be “a big price to pay” for the chemical weapons attack, raised questions about whether Israel was acting alone or as a proxy for the United States. Israel typically does not comment on its airstrikes in Syria.

It was the second such attack this year on the air base, known as T4, where Iranian fighters are believed to be stationed.

Russia’s Defense Ministry said two Israeli aircraft targeted the T4 air base, firing eight missiles. It said Syria shot down five of them while the other three landed in the western part of the base. Syrian state TV quoted an unnamed military official as saying that Israeli F-15 warplanes fired several missiles at T4. It gave no further details.

Israel’s Foreign Ministry had no comment when asked about reports of the airstrikes.

Since 2012, Israel has struck inside Syria more than 100 times, mostly targeting suspected weapons convoys destined for the Lebanese militant group Hezbollah, which has been fighting alongside Syrian government forces.

Israel hit the T4 base in February, after it said an Iranian drone that had violated Israeli airspace took off from the base. The base, which was used as a launching pad for attacks against Islamic State militants who were at one point stationed nearby, is near the Shayrat air base, which was targeted by U.S. missiles last year in response to a chemical weapons attack.

Saturday’s suspected gas attack took place in the town of Douma, the last remaining rebel bastion in the eastern suburbs of Damascus. It killed entire families in their homes and underground shelters, opposition activists and local rescuers said.

Syria’s state news agency SANA initially said the attack on the T4 air base was likely “an American aggression,” but the Pentagon denied involvement, and the agency then dropped the accusation, blaming Israel instead. SANA said the missile attack resulted in a number of casualties, but provided no specific figures.

Iran’s semi-official Fars news agency identified three Iranians it said were among those killed. It did not provide their ranks or further information.

The Britain-based Syrian Observatory for Human Rights, which monitors the war through a network of activists on the ground, said 14 died, including Iranians and three Syrian officers.

Rami Abdurrahman, the Observatory’s chief, said the assault targeted a mobile air defense unit and some buildings inside the air base. He said it also hit posts outside the base used by the Iranians and Iran-backed fighters.

Dmitry Peskov, spokesman for President Vladimir Putin, told reporters on Monday that Israel had not notified Russia of the airstrike, even though there may have been Russian military advisers at the base, which he described as “a cause for concern for us.”

The U.S. launched several dozen Tomahawk cruise missiles at a Syrian air base after a chemical attack in the northern town of Khan Sheikhoun killed dozens of people almost exactly a year ago.

In response to Saturday’s reported attack, Trump on Sunday blamed Syrian government forces for what he called a “mindless CHEMICAL attack.” In a series of tweets, he held Russia and Iran, Assad’s chief sponsors, responsible.

Trump was to meet with his senior military leadership on Monday, the same day his new national security adviser, John Bolton, assumes his post. Bolton has previously advocated significant airstrikes against Syria.

The European Union also laid the blame squarely on Assad’s government.

The Syrian government denied the chemical weapons allegations, calling them fabrications. The Russian military said its officers visited the hospital in Douma and talked to the staff, and said they did not confirm reports of the assault.

First responders entering apartments in Douma late Saturday said they found bodies collapsed on floors, some foaming at the mouth. The opposition’s Syrian Civil Defense rescue organization said the victims appeared to have suffocated.

The organization, also known as the White Helmets, and the Syrian American Medical Society, a medical relief organization, did not identify the substance used but said survivors treated at clinics smelled strongly of chlorine.

Those reports could not be independently verified because of a government blockade around the town.

Hours after the attack, the Army of Islam rebel group agreed to surrender the town and evacuate its fighters to rebel-held northern Syria, Syrian state media reported. The group also agreed to release its prisoners, a key government demand.

More than 100 buses entered the town on Sunday night to take the fighters and their families to Jarablus, a town under the shared control of Turkish troops and allied Syrian forces, said Syrian state-affiliated al-Ikhbariya TV.

Syrian state TV said two buses left early Monday and that 11 more buses were getting ready to move.

Syrian state media said dozens of civilians who had been held for years by the rebels were set free.

The evacuations follow a pattern of departures around the capital, Damascus, and other major Syrian cities as the government reasserts its control after seven years of war.

In his tweets Sunday, Trump called Assad an “animal” and delivered a rare personal criticism of Putin for supporting him. Trump has declared his intent to withdraw U.S. troops from Syria in the coming months, despite resistance from many of his advisers.

Syrian rescuers from the White Helmets documented 42 fatalities in Saturday’s reported chemical attack but were impeded from searching further by strong odors that caused breathing difficulties, said Siraj Mahmoud, a spokesman for the group.

More than 500 people, mostly women and children, were brought to medical centers complaining of difficulties breathing, foaming at the mouth and burning sensations in the eyes. Some had bluish skin, a sign of oxygen deprivation, according to a statement. The symptoms are consistent with chemical exposure.

Douma is part of the eastern Ghouta suburbs, where a 2013 chemical attack killed hundreds of people and was widely blamed on the government. The U.S. threatened military action but later backed down.

Syria denies ever using chemical weapons during the war and says it eliminated its chemical arsenal under a 2013 agreement brokered by the U.S. and Russia.